Vapor-phase Synthesis And Photoluminescence Properties Of ZnO And Doped ZnO Nanostructures

Quasi-one-dimensional (1D) nanomaterials, including nanowires, nanorods, nanopins, nanotubes, nanobelts, nanocables, heterojunction, etc, are attracting considerable attention recently. Among these materials, functional oxide semiconductor nanomaterials are especially popular, because not only various nanostructures have been synthesized, but also the nanodevices based on these nanostructures can be widely used in optics, electronics, magnetism, gas sensing and field emitting. Although the research of 1D oxide semiconductor nanomaterials has already made much progress, it still remains a significant challenge to achieve controlled synthesis of desired morphologies, components and structures. This paper is mainly focused on the controllable synthesis and optical properties of ZnO based 1D nanomaterials:1. Synthesis and Photoluminescence of ZnO Comb-Like StructureHigh-density single crystal Zinc oxide (ZnO) comb-like structures are synthesized on silicon substrate via thermal evaporation process without any metal catalyst. The structure, growth mechanism, and optical properties of the structures are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. These comb-teeth, with a diameter about 20 run, growing along [0001] direction have a well-defined epitaxial relationship with the comb ribbon. TEM reveals that there are a few non-periodic zigzag notches on the both sides of the comb-teeth. Room temperature photoluminescence measurements under excitation at 325nm show that the ZnO comb-like nanostructure has a weak UV emission at around 384nm and a strong green emission around 491nm, which correspond to a near band-edge transition and the singly ionized oxygen vacancy, respectively.2. Controllable synthesis and photoluminescence properties of ZnO nanorod and nanopin arraysWell-aligned ZnO nanorods and nanopins are synthesized on a silicon substrate using a one-step simple thermal evaporation of a mixture of zinc and zinc acetate powder under controlled conditions. A self-assembled ZnO buffer layer was first obtained on the Si substrate. SEM images show the diameter of the both ZnO nanostructures are between 150 to 200nm and up to several micrometers. The TEM images reveal the both ZnO nanostructures are single crystal and grow along the [0002] direction. The influence of the background atmosphere on the two ZnO nanostructures has been studied. Two different growth mechanisms are mentioned to interpret the formation of ZnO nanorod and nanopin arrays in our work. The room temperature PL features the ZnO nanorods exhibit only sharp and strong ultraviolet (UV) emission emissions, which confirms the better crystalline and optical quality than the ZnO nanopins.3. Self-Assembled Growth and Photoluminescence Properties of Single Crystalline ZnGa₂O₄ Superlattice NanowiresUniform zinc gallate (ZnGa₂O₄) nanowires with superlattice structure are successfully synthesized by one-step simple thermal evaporation of a mixture of Zn and Ga powders under controlled conditions. It is found there is superlattice structure existing in the ZnGa₂O₄ nanowirs. A vapor-solid (VS) formation mechanism is mentioned to interpret the self-assembled growth of ZnGa₂O₄ superlattice structure in our work. The room-temperature photoluminescence spectrum of ZnGa₂O₄ nanowires features three blue peaks around 421, 443, and 472nm, which are attributed to self-activation center of the octahedral Ga-O, electronic transitions of localized Ga³⁺ ion in the octahedral Ga-O and the recombination of a trapped exciton. The peaks have the obvious blue shifts, which corresponds to the existing of quantum well in the superlattice.